The scientific study of meditation and psychedelic drugs has seen remarkable developments in recent years. The increased focus on meditation in cognitive neuroscience has led to a cross-cultural classification of standard meditation styles validated by functional and structural neuroanatomical data (A. Lutz et al. 2008; K. C. R. Fox et al. 2016; Dahl, Lutz, and Davidson 2015). Meanwhile, the renaissance of psychedelic research (Carhart-Harris and Goodwin 2017) has shed light on the neurophysiology of altered states of consciousness induced by classical hallucinogens, such as psilocybin and LSD, whose effects are mainly mediated by agonism of serotonin receptors, and the serotonin 2A receptor subtype specifically (Nichols 2016; Carhart-Harris et al. 2012; Carhart Harris, Muthukumaraswamy, et al. 2016). However, few attempts have been made at bridging these two domains of inquiry, despite increasing evidence of overlap between the phenomenology and neurophysiology of meditation practices and psychedelic states. In particular, many contemplative traditions explicitly aim at dissolving the sense of self by eliciting altered states of consciousness through meditation (J.H. Austin 2000; Dahl, Lutz, and Davidson 2015; Vago and Silbersweig 2012; Josipovic 2010), while classical psychedelics are known to produce significant disruptions of self-consciousness, a phenomenon known as “drug-induced ego dissolution” (DIED; Nour and Carhart-Harris 2017; Millière 2017).
In this article, we discuss available evidence regarding convergences and differences between phenomenological and neurophysiological data on meditation practice and psychedelic drug-induced states, with a particular emphasis on alterations of self-experience. While both meditation and psychedelics are suspected to disrupt self-consciousness and its underlying neural processes, this general hypothesis requires careful qualification. First, it is important to emphasize right away that neither meditation nor psychedelic states can be conceived as simple, uniform categories. Many variables modulate the subjective effects of contemplative practice and psychedelics, including the style of meditation or the drug and dosage used, as well as personal factors such as level of experience and personality traits. In particular, dramatic disruptions of self-consciousness seem to occur mostly for highly experienced meditators or with high doses of psychedelics. Thus, we suggest that both meditation and psychedelics can induce a wide variety of global states of consciousness, but these states are sensitive to a multitude of factors in addition to the specific inducers we are highlighting here.
In addition, we suggest that there are important phenomenological differences even between conscious states described as experiences of self-loss. As a result, we propose that self consciousness may be best construed as a multidimensional construct, and that “self-loss” or “ego dissolution”, far from being an unequivocal phenomenon, can take several forms. Indeed, various aspects of self-consciousness, including narrative aspects linked to autobiographical memory, self related thoughts and mental time travel, and embodied aspects rooted in multisensory processes, may be differently affected by psychedelics and meditation practices. It is also worth acknowledging *corresponding authors By “self-consciousness”, we refer in this article to a subject’s consciousness of themselves – also called “sense of self”, “self-awareness”, “phenomenal selfhood” or “self-experience”. Importantly, “self-consciousness” does not refer here to the social awareness of being the object of the observation of others. From a methodological perspective, disruptions of self-consciousness induced by meditation might be more challenging in terms of laboratory production, while disruptions of self-consciousness following the administration of psychedelic drugs might be more strictly dose-dependent and therefore easier to produce in a controlled setting. In a similar vein, the choice of baseline conditions and control groups is a multi-faceted issue in meditation research, often limiting interpretability, whereas placebo-controlled designs are the default for studies on psychedelics. Nonetheless, true placebo control is difficult to achieve with psychedelics, given their vivid and characteristic subjective effects.
Provisional that “self-loss” or “ego dissolution” may be a non-linear phenomenon that only occurs after a critical inflection point has been reached. Finally, we consider long-term outcomes of experiences of self-loss induced by meditation and psychedelics on individual traits and prosocial behavior. We call for caution regarding the problematic conflation of temporary states of self-loss with “selflessness” as a personal or social trait, although it remains possible that correlations exist between short term experiences and long term dispositions in this regard.